Habitable Zones & Global Climate: August 2013

The characterization of the atmospheres of habitable-zone Earth-mass exoplanets that transit across main-sequence stars, let alone the detection of bio-markers in their atmospheres, will be challenging even with future facilities. It has been noted that white dwarfs (WDs) have long-lived habitable zones and that a large fraction of WDs may host planets.

If water is the source of life, then finding the source of water certainly qualifies as a worthy astrobiological endeavor. Scientists have formulated certain scenarios for how our planet became wet and stayed wet, but other planets may not have been able to tap this same source.

The problem of the contribution of cosmic rays to climate change is a continuing one and one of importance. In principle, at least, the recent results from the CLOUD project at CERN provide information about the role of ionizing particles in 'sensitizing' atmospheric aerosols which might, later, give rise to cloud droplets.

During vast ice ages millions of years ago, sheets of glaciers stretched from the poles almost to the equator, covering the Earth in a frozen skin. Conditions on the "snowball Earth," as scientists refer to it, made the planet a completely different place.

A lot of people mix up the ozone hole and global warming, believing the hole is a major cause of the world's increasing average temperature. Scientists, on the other hand, have long attributed a small cooling effect to the ozone shortage in the hole.